The present invention pertains to the field of jet technology, primarily to vacuum jet apparatuses being used in various processes for evacuation of gas-vapor mediums. A vacuum jet apparatus, with a nozzle for discharge of an active steam medium, a mixing chamber and a diffuser, is known (see German patent No. 51229, H cl. 59c, 13, 1890).
However, this jet apparatus has a low efficiency factor. As a consequence, a large input of energy is necessary for creating reduced pressure with this device.
The closest analogue selected by the authors as the starting point for this invention, is a liquid-gas jet apparatus, containing a nozzle with a branch pipe for delivery of an active liquid medium and a mixing chamber (see, for example, U.S. Pat. No. 2,632,597, H cl., 417-196, 1953).
This jet apparatus is rated for a relatively low mass flow of an active liquid and, due to the scaling factor effect, the apparatus is not effective when a high mass flow of the active liquid is necessary.
The technical problem to be solved by this invention is an increase in reliability of a liquid-gas jet apparatus by providing a more steady stream of an active liquid medium and reducing energy losses during interaction of the active (ejecting) medium with a passive (ejected) medium.
The above mentioned problem is solved as follows: a nozzle of a liquid-gas jet apparatus, where the liquid-gas jet apparatus has a nozzle for feed of an active liquid medium and a mixing chamber, has a central channel and a peripheral annular channel. The total surface area of the outlet cross-section of the nozzle is determined from the following formula:
S=Sxcexc(1+{square root over ((Skc/Sxcexc)3)}),
where
Sxe2x80x94is the total surface area of the outlet cross-section of the nozzle (i.e. the total surface area of the outlet cross-sections of the central and peripheral channels);
Sxcexcxe2x80x94is the surface area of the outlet cross-section of the central channel of the nozzle;
Skcxe2x80x94is the surface area of the minimal cross-section of the mixing chamber.
The outlet cross-section of the central channel of the nozzle can lie in the plane of the outlet cross-section of the annular peripheral channel, or the outlet cross-section of the peripheral channel can be shifted in the counter-flow direction relative to the outlet cross-section of the central channel.
It was discovered that the nozzle for feed of an active liquid medium composed of a central channel and a peripheral annular channel ensures more effective use of the energy of the active liquid medium due to a reduction of energy losses during interaction between the active (ejecting) and passive mediums. Primary contact of the active and passive streams is accompanied by energy interchange between the streams, which is why discharge of the ejecting medium through the peripheral annular channel reduces kinetic energy losses during interaction of the streams.
In addition, availability of two jets of the active medium causes significant expansion of a peripheral unstable (turbulent) area of the active medium stream. This promotes creation of a zone of gradual increase of kinetic energy of the passive gaseous medium from the peripheral to the central area of the stream. This is especially important in the case of evacuation of a gas-vapor medium. When relatively large (in comparison with gas molecules) drops of condensate of the vapor phase of the evacuated gas-vapor medium get into the unstable (turbulent) zone of the active medium stream, loss of kinetic energy is minimal because in this zone the drops are accelerated without disintegration. Experiments showed that the optimal ratio between the surface areas of the central and peripheral channels of the nozzle and the surface area of the minimal cross-section of the mixing chamber is of great importance for effective implementation of the above described mode of mixing of the streams of active liquid and passive gas-vapor mediums.
It was determined that for the liquid-gas jet apparatuses with various rated performances, the most reasonable Skc/Sxcexc ratio ranges from 10 to 78 and the most reasonable Skc/S ratio ranges from 2.4 to 7.93.
In particular circumstances the relative spatial position of the outlet cross-sections of the central and peripheral channels of the nozzle is of great importance for the effective functioning of the liquid-gas jet apparatus. The most common case is when the outlet cross-sections of the central and peripheral channels are located in the same cross-sectional plane. However, in some cases there is a high content of easy-condensable vapors in the evacuated gaseous medium and consequently there are many dispersed liquid drops in it. In such cases it is advisable to shift the outlet cross-section of the peripheral channel in the counter-flow direction in order to prolong the time of contact of the active and passive mediums and to accelerate the passive medium gradually with minimal losses of kinetic energy during its interaction with the active stream.
So, the introduced design of the liquid-gas jet apparatus provides a solution to the stated technical problem, i.e. the jet apparatuses of the introduced design exhibit an improved operational reliability and a higher efficiency during evacuation of various gas-vapor mediums.